A proton NMR spectrum will often include information on the relative peak integrals. These are the relative areas under each signal in the spectrum, and they are correlated with the number of protons that give rise to the signal. We can therefore use peak integrals to determine the relative number of protons in each signal. See example here in Figure 1.

4 peaks overall, peak at 0.9ppm a triplet with integral 3, 1.9 ppm a sextet with integral value 2, singlet at 2.1 ppm with integral value 3, triplet at 4.1 ppm with integral value 2. Next to each integral value is a rectangle with length equal to the spread of the peak.

Figure 1. Example of proton NMR spectrum, including relative integral numbers above each peak.

For a splitting pattern, the entire signal is usually included in the integral.

It's key to realise that the integrals are relative, and does not necessarily express the exact number of protons. From the integrals in Figure 1, one might conclude that each signal represents either 2 or 3 protons. But from the integrals alone, the reality might just as well be 4 and 6 protons, or 6 and 9 protons. So while the integrals provide useful information, they can often not stand alone in elucidating a structure.